The present invention relates to a hermetic motor compressor for compressing refrigerant in air conditioners, refrigerators or the like. In air conditioners or refrigerators, a closed circuit of refrigerant is formed by successively connecting a refrigerant compressor, condenser, pressure reducer and an evaporator.
Compressed refrigerant gas discharged from the refrigerator compressor is cooled and liquefied in the condenser and flows through the pressure reducer into the evaporator where it absorbs heat from a fluid to be cooled so as to be evaporated. The refrigerant then flows back to the compressor to complete one cycle of operation. The fluid to be cooled is cooled as a result of heat absorption in the evaporator and is used as a cold heat source for air conditioners or refrigerators.
Hermetic motor compressors are broadly used as a refrigerant compressor. This hermetic motor compressor has a closed container or housing which houses an electric motor and a compressor integrally connected to each other. Since the closed housing thermally insulates its interior from the outside, the temperature of the compressor is raised to a high level to undesirably heat surrounding refrigerant gas in the closed housing. In consequence, the refrigerant gas of low temperature, which has returned from the evaporator of the refrigerant circuit to temporarily stay in the closed housing is heated by the heat generated by the compressor, so that the cylinder of the compressor is made to suck the refrigerant of a high temperature and, hence, a large specific volume. Consequently, the weight rate of the refrigerant gas flow sucked by the cylinder of the compressor is reduced to lower the volumetric efficiency of the compressor, which in turn results in lowering the refrigeration power per unit input power. The refrigerant gas which is delivered into the closed housing through a refrigerant return pipe is heated by the heat radiated from the discharge pipe of high temperature, discharge silencer, head cover and other parts of high temperature to be increased in its specific volume, so that the weight of the refrigerant gas displaced by a particular cylinder is decreased to deteriorate the performance of the compressor and to pose various other problems.
In order to obviate the above-described shortcomings of the prior art, it has been proposed to limit the heat radiated from the discharge pipe.
For instance, U.S. Pat. No. 3,926,009 discloses a hermetic compressor in which, a double-walled discharge tube that is insulated so as to prevent undesirable heat transfer between the discharge tube and the cool refrigerant as well as heat transfer between the discharge tube and the lubricant and in which, said discharge tube has one or both of inner and outer tublar members corrugated to prevent transmission of vibration from the compressor to the closed housing. In this hermetic compressor, heat insulating means is provided only for the discharge tube, and no specific consideration is given to the thermal insulation of the silencer and head cover.
Japanese Patent Publication No. 18061/1971 discloses a hermetic compressor having means for thermally insulating the discharge tube and discharge silencer thereby to lower temperature in the closed housing. More specifically, this thermal insulating means includes a heat insulating layer or foil provided around the discharge tube and discharge silencer to reduce heat radiation from the tube to the interior of the closed housing. The discharge tube is in the form of hose to absorb vibration of the compressor. The heat insulation layer is closely adhered to the outer surface of the discharge tube and discharge silencer.